Closed captioning or subtitling is the process of displaying text on a television, video screen or other visual display to provide additional or interpretive information to individuals who wish to access it. Closed captions typically show a transcription of the audio portion of a program as it occurs (either verbatim or in edited form), sometimes including non-speech elements. For live programs, spoken words comprising the television program's soundtrack are typically transcribed by a human operator (a speech-to-text reporter) using stenotype or stenomask type machines, whose phonetic output is translated into text by a computer and displayed on the screen. In some cases, a transcript is available beforehand and captions are simply displayed during the program after being edited. For programs that have a mix of pre-prepared and live content, such as news bulletins, a combination of the above techniques may be used. For prerecorded programs, commercials, and home videos, audio is often transcribed and captions are prepared, positioned, and timed in advance.